Abstract: The emulsifying activity index (EAI) and stability of soybean protein isolate (SPI)-stabilized emulsions containing water-soluble polysaccharide from soybean hull extracted by microwave-assisted extraction were investigated with respect to three variables: microwave power, irradiation time and solid-to-solvent ratio. The EAI of emulsions increased first and then decreased with microwave irradiation time, but always increased with increasing microwave power. The interaction between microwave irradiation time and solid-to-solvent ratio had a significant effect on the EAI. The absolute value of Zeta potential increased first and then decreased with the increase of microwave power. A microwave power of 480 W, an irradiation duration of 35 min, and a solid-to-solvent ratio of 1:20 (g/mL) were found to be the optimum conditions to obtain a higher EAI of 46.15 m2/g and a higher absolute value of Zeta potential of 34.3 mV compared to 16.31 m2/g and 21.5 mV observed for the SPI-stabilized emulsion without the polysaccharide extracted from soybean hull. The results of this study provide a basis for the industrial preparation of soybean hull polysaccharide to be used as an emulsion stabilizer.

Key words: soybean hull polysaccharide, microwave-assisted extraction, emulsifying activity, emulsion stability